Aqueous fluorine-containing rubber coating composition and article coated therewith

ABSTRACT

An aqueous fluorine-containing rubber coating composition comprising (a) fluorine-containing rubber, (b) fluorine-containing resin, (c) an aminosilane compound of the formula: ##STR1## wherein R is methyl or ethyl; X is a single bond or --(CH 2 ) 2  --NH--, --CONH-- or --(CH 2 ) 2  --NH--(CH 2 ) 2  --NH--; and n is 2 or 3, and (d) an aqueous liquid vehicle, the weight ratio of the component (a) and the component (b) being from 95:5 to 35:65, which makes the resultant coating film non-adherent and more lubricous.

The present invention relates to an aqueous fluorine-containing rubbercoating composition and an article coated therewith. More particularly,it relates to an aqueous coating composition comprising afluorine-containing rubber, a fluorine-containing resin, an aminosilanecompound and an aqueous liquid vehicle, and an article at least partlycoated with said coating composition.

Since a fluorine-containing rubber has good resistance to heat, weather,oils, solvents and chemicals, a coating composition comprising the sameis widely used for coating various kinds of substrates such as metals,plastics, rubbers, fabrics, non-woven fabrics and fibers.

It was previously found that the incorporation of an aminosilanecompound bearing an amino group at the molecular end into afluorine-containing rubber coating composition is effective inimprovement of various properties of such composition. Thus, theresulting composition is not gelled and has an excellent self adhesivityto a substrate with a long pot life. Further, it can be used for spraycoating without cobwebbing even when the fluorine-containing rubbercontent is high (cf. Japanese Patent Publication (unexamined) No.28249/1981). Furthermore, it can afford a coating film excellent inmechanical properties, particularly tensile strength by incorporatingtherein an amine compound having at least one amino group directlybonded to an aliphatic hydrocarbon group (cf. Japanese PatentPublication (unexamined) No. 47455/1981).

As a result of the extensive study to improve non-adhesiveness andlubricity of a coating film formed from the said fluorine-containingrubber coating composition, it has been found that the incorporation ofa certain specific amount of a fluorine-containing resin into suchcomposition is effective to make the resultant coating film non-adherentand more lubricous. It has also been found that the additionalincorporation of an inorganic fibrous material therein is effective inimprovement of the recovery of the resulting coating film fromcompression.

According to the present invention, there is provided an aqueousfluorine-containing rubber coating composition comprising (a) afluorine-containing rubber, (b) a fluorine-containing resin, (c) anaminosilane compound of the formula: ##STR2## wherein R is methyl orethyl, X is a single bond or --(CH₂)₂ --NH--, --CONH-- or --(CH₂)₂--NH--(CH₂)₂ --NH-- and n is 2 or 3, and (d) an aqueous liquid vehicle.Optionally, an inorganic fibrous material, an amine compound having atleast one amino group directly bonded to an aliphatic hydrocarbon group,etc. may be incorporated therein.

The reason why the incorporation of the fluorine-containing resinimproves the non-adhesiveness and lubricity of the coating film withoutany substantial influence on the adhesivity to the substrate as well asthe mechanical properties is presumed as follows: thefluorine-containing resin which per se has non-adhesiveness andlubricity concentrates near the surface of the coating film so that saidperformances of the fluorine-containing resin appear on the surface ofthe coating film without reducing the adhesivity to the substrate andmechanical properties. In fact, it was confirmed by X-ray fluorometrythat the fluorine content of the coating film of 50μ thick cured at 300°C. for 30 minutes at the surface is about 1.5 times that of said coatingfilm at the bonded face to the substrate. Higher curing temperaturestend to give greater differences in the fluorine content between them.

The fluorine-containing rubber (a) is a highly fluorinated elasticcopolymer, preferably comprising about 40 to 85% by mol of units ofvinylidene fluoride and about 60 to 15% by mol of units of at least oneof other fluorine-containing ethylenically unsaturated monomerscopolymerizable therewith. As the fluorine-containing rubber (a), theremay be also used any fluorine-containing rubber bearing iodine on thepolymer chain, preferably an elastic copolymer which bears about 0.001to 10% by weight, particularly about 0.01 to 5% by weight of iodine, andcomprises about 40 to 85% by mol of units of vinylidene fluoride andabout 60 to 15% by mol of units of at least one of otherfluorine-containing ethylenically unsaturated monomers copolymerizabletherewith (cf. Japanese Patent Publication (unexamined) No. 40543/1977).Specific examples of the fluorine-containing ethylenically unsaturatedmonomers as above stated are hexafluoropropylene, pentafluoropropylene,trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, vinylfluoride, perfluoro(methyl vinyl ether), perfluoro(ethyl vinyl ether),perfluoro(propyl vinyl ether), etc. Among various fluorine-containingrubbers, preferred are vinylidene fluoride/hexafluoropropylenecopolymer, vinylidene fluoride/tetrafluoroethylene/hexafluoropropylenecopolymer, etc.

Generally, the fluorine-containing rubber is used in the form of anaqueous dispersion. The aqueous dispersion may be an emulsion comprisingthe fluorine-containing rubber, which is obtainable by emulsionpolymerization of the said monomers. Alternatively, the aqueousdispersion may be the one obtained by subjecting the said monomers tosuspension or bulk polymerization or the like and dispersing theproduced fluorine-containing rubber into an aqueous medium, ifnecessary, with previous pulverization and/or by the aid of anysurfactant. The aqueous dispersion may contain from 10 to 70% by weight,preferably from 30 to 60% by weight of the fluorine-containing rubber.Such concentration can be suitably controlled by concentration ordilution. In addition to the surfactant, other conventional additivessuch as pigments, acid acceptors and fillers may be incorporated intothe aqueous dispersion.

As the fluorine-containing resin (b), there are usablepolytetrafluoroethylene, copolymers of tetrafluoroethylene and at leastone of other ethylenically unsaturated monomers such as olefins (e.g.ethylene, propylene), haloolefins (e.g. hexafluoropropylene, vinylidenefluoride, chlorotrifluoroethylene, vinyl fluoride) and perfluoro(alkylvinyl ethers), polychlorotrifluoroethylene, polyvinylidene fluoride,etc. Preferred fluorine-containing resins are polytetrafluoroethylene,copolymers of tetrafluoroethylene and at least one ofhexafluoropropylene, perfluoro(methyl vinyl ether), perfluoro(ethylvinyl ether) and perfluoro(propyl viny ether), usually the content ofthese monomers being not more than 40% by weight based ontetrafluoroethylene, etc.

In general, the fluorine-containing resin is used in the form of anaqueous dispersion. The aqueous dispersion may be an emulsion obtainedby emulsion polymerization of the said monomers or a dispersion obtainedby subjecting the said monomers to suspension or bulk polymerization anddispersing the produced resin into an aqueous medium, if necessary, withprevious pulverization and/or by the aid of any surfactant.

The aminosilane compound (I) as the component (c) not only serves as acuring agent of the fluorine-containing rubber but also contributes toimprovement of the adhesivity of the coating film. Specific examples ofthe aminosilane compound (I) are γ-aminopropyltriethoxysilane(hereinafter referred to as "A-1100"),N-β-aminoethyl-γ-aminopropyltrimethoxysilane,N-(trimethoxysilylpropyl)ethylenediamine,N-β-aminoethyl-γ-aminopropylmethyldimethoxysilane,β-ureidopropyltriethoxysilaneβ-aminoethyl-β-aminoethyl-γ-aminopropyltrimethoxysilane, etc.

The aqueous vehicle (d) may be water or a mixture of water with anywater-miscible organic solvent. Examples of the water-miscible organicsolvent include alcohols such as methanol, ethanol, propanol,ethyleneglycol, carbitol and cellosolve.

In addition to the above essential components (a) to (d), the coatingcomposition of the invention may comprise optionally the inorganicfibrous material. Inclusion of the inorganic fibrous material ispreferred for enhancing the recovery from compression. Examples of theinorganic fibrous material are glass fibers, carbon fibers, asbestosfibers, fibrous potassium titanate, etc. The average length of theinorganic fibrous material may be at least 1μ, preferably from 1 to100μ.

The amino compound having at least one terminal amino group directlybonded to an aliphatic hydrocarbon group, which serves as a curing agentof the fluorine-containing rubber and also improves the mechanicalproperties of the coating film, may be incorporated in the coatingcomposition as an optional component. Specific examples of the aminocompound include monoamines (e.g. ethylamine, propylamine, butylamine,benzylamine, allylamine, n-amylamine, ethanolamine), diamines (e.g.ethylenediamine, trimethylenediamine, tetramethylenediamine,hexamethylenediamine,3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro-[5,5]undecane (hereinafterreferred to as "V-11")) and polyamines (e.g. diethylenetriamine,triethylenetetraamine, tetraethylenepentaamine, pentaethylenehexaamine).Among them, those having at least two terminal amino groups areparticularly preferred.

The coating composition of the invention may be prepared, for instance,by adding the aminosilane compound (I) and, if necessary, the aminecompound to a mixture of the aqueous dispersions of thefluorine-containing rubber and of the fluorine-containing resin,followed by agitation to make a uniform mixture. Optional additives suchas a pigment, an acid acceptor and a filler may be added previously tothe mixture of the aqueous dispersions and/or ultimately to a mixture ofthe other components.

When the aminosilane compound (I) is added directly to the aqueousdispersion of the fluorine-containing rubber, the resultant mixture maybecome viscous to cause partial gellation. In order to prevent thisgellation, it is preferred that the aminosilane compound is partly orcompletely hydrolized with water prior to its addition.

The weight ratio of the fluorine-containing rubber and thefluorine-containing resin may be usually from 95:5 to 35:65. When thecontent of the fluorine-containing resin is less than the lower limit,the non-adhesiveness and/or lubricity of the coating film are notsatisfactorily improved. When the content is more than the upper limit,the coating film having a desired non-adhesiveness is hardly obtainableand cracks or pinholes tend to be formed.

The amount of the aminosilane compound (I) may be usually from 1 to 30parts by weight, preferably from 1 to 20 parts by weight to 100 parts byweight of the fluorine-containing rubber. When the amine compound isadded, the total amount of the aminosilane compound (I) and the aminecompound may be within the above range, the molar ratio of the formerand the latter being from 1:99 to 90:10.

The acid acceptor as one of the optional components may be aconventional one as used in curing the fluorine-containing rubber.Examples are oxides and hydroxides of divalent metals (e.g. magnesium,calcium, zinc, lead). As the filler, there may be exemplified silica,clay, diatomaceous earth, talc, carbon, etc.

The coating composition of the invention may be applied onto a substrateby a conventional procedure (e.g. brushing, dipping, spraying) and curedat a temperature usually of from room temperature to 400° C., preferablyof from 100° to 400° C. for an appropriate period of time to give acoating film.

The fluorine-containing rubber coating film thus formed has excellentproperties inherent to the fluorine-containing rubber and also hasexcellent adhesivity to the substrate and good mechanical properties,particularly tensile strength. Further, the coating film is providedwith non-adhesiveness and lubricity at the surface.

Accordingly, the coating composition of the invention can be usedeffectively to make a coating film, for which non-adhesiveness andlubricity are required. For example, the coating composition may becoated on various gaskets, especially those made of metals such as iron,aluminum, copper and their alloys; packings; valve stem seals and leadvalves in automobiles; rubber-made seal rings of hydraulic equipments;rolls for printing, weaving and paper machines; mixing rolls; bathes andblades for mixing of coating compositions; conveying belts for rubber orresin molds; belts for printing; belts for high-frequency heating;diaphragm; doctor knives and guides in decoloring, dying and washingsteps in fiber or paper industry; rubber-made coupling members fordomestic mixers; molds for molding resins; washing fixtures forprecision machines; plating bathes or rinsing bathes; inner surfaces offuel containers and chemical tanks; surfaces of resin or rubber linings;wires, etc. Also, it may be used for electro-conductive coating.

Metal gaskets for compressors in automobile coolers coated with aconventional fluorine-containing rubber coating composition have manydisadvantages due to its adhesiveness to a sealing surface such as badworkability when the gasket is disassembled for replacement of the wearparts of the compressors, nonreusability of the disassembled gaskets andpoor sealing properties due to the adhered residual rubber when the newparts are assembled. These disadvantages are, however, overcome by themetal gaskets coated with the coating composition of the invention dueto their non-adhesiveness at the surface. The disassembled gaskets aresufficiently reusable.

The invention will now be illustrated, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a sectional view of a swash plate type compressor to be usedfor an automobile cooler, and

FIG. 2 is a front view of a gasket to be used for the swash plate typecompressor.

FIG. 1 shows a swash plate type compressor, in which each end of a pairof cylinder blocks 1F, 1R which longitudinally abut each other isrespectively sealed with a front housing 4F and a rear housing 4Rprovided with valve plates 3F, 3R between the cylinder blocks and thehousing. A driving shaft 16 is rotatably supported by the cylinderblocks 1F, 1R and extends through the most part of the central portionof the cylinder blocks. One end of the shaft 16 extends through andbeyond the housing 4F and may be connected with a power source, and theoutwardly extending part of the shaft 16 is provided with a shaftsealing member 50 in order to maintain airtightness. An adequate numberof pairs of cylinder bores 2F, 2R are formed in the cylinder blocks inparallel with the driving shaft 16 on a circumference a center of whichis the center of the driving shaft 16. Pistons 20 inserted in thecylinder bores 2F, 2R are engaged with a swash plate 17 slantingly fixedto the driving shaft 16 through bearings such as shoes 18 and balls 19.In the valve plates 3F, 3R, intake ports 31 and exhaust ports 32 whichcorrespond to the cylinder bores 2F, 2R are perforated. Intake valvesheets 33 provided with intake lead valve members which can open andclose the intake ports are held between the cylinder blocks 1F, 1R andthe valve plate 3F, 3R respectively. Exhaust valve sheets 21 providedwith exhaust lead valve members 21A which can open and close the exhaustports are held between the housings 4F, 4R and the valve plates 3F, 3Rrespectively together with gasket 100, later described in detail, whichis overlaid on the exhaust valve sheets and presses the exhaust valves.Within the interiors of the housings 4F, 4R, there formed a devidedintake rooms 6F, 6R and exhaust rooms 5F, 5R which can communicate withthe cylinder bores 2F, 2R through the intake ports 31 and the exhaustports 32 respectively and also can communicate with an intake part andan exhaust part of an outer cooling circuit through a conventionalmember (not shown). Numeral 8 represents a clamping bolt which maintainsthe compressor assembled.

Hereinafter, the gasket 100 and the exhaust valve sheet 21 are describedin detail.

In FIG. 2, the exhaust valve sheet 21 comprises a base ring 21 B and theradially protruded exhaust lead valve members 21A corresponding to theexhaust ports 32. The gasket 100 comprises (a) the first ring member 104corresponding to interstructures 41F, 41R which separate the base ring21B of the exhaust valve sheet 21 from the inner side of the exhaustroom 41F, 41R of the housing 4F, 4R; (b) the second ring member 103corresponding to interstructures 42F, 42R which separate the exhaustroom 5F, 5R from the intake room 6F, 6R; (c) the third ring member 105corresponding to the interstructures 43F, 43R which separate the outerside of the intake rooms 6F, 6R from the exterior of the compressor; (d)the rib members 106 bridging the second ring member 103 and the thirdring member 105 at appropriate positions; and (e) and the rib members107 bridging the first ring member 104 and the second ring member 103 atpositions corresponding to the exhaust, lead valve members 21A of theexhaust valve sheet 21. The rib members 107 are bent such that the ribmembers 107 part more widely from the exhaust lead valve members 21A atthe top of the latter and being constructed so as to act as retainerswhich restrain the deformation of the exhaust lead valve members 21A.

The coating composition of the invention is coated on the surface of thegasket 100 with even thickness of 20 to 50μ by a conventional methodsuch as dipping and spray coating. The gasket may be prepared byprecoating the coating composition of the invention on a plate materialand blanking pressing the plate material to obtain a desired formgasket. Preferably, the gasket is prepared by first blank pressing theplate material without coating and then coating the coating compositionon the pressed material. The latter process has advantages such thatsince the rupture cross-sections are coated with the coatingcomposition, peeling of the film and rusting of the metal base materialare prevented. The base material may be plate material made of metalsuch as iron, aluminum and copper and their alloys and plate materialmade of rigid plastics.

In the swash plate type compressor constructed as above, the pressedparts of the gasket 100, i.e. the first ring member 104, the second ringmember 103 and the third ring member 105 are tightly sealed with thecoating composition coated on the both surfaces. During the operation ofthe compressor, the driving shaft 16 is rotated with driving forcetransmitted from the outer power source, then the pistons 20 reciprocatein the cylinder bores 2F, 2R with the rotation of the swash plate 17,and intake, compressing and exhaust functions are effected. Details areas follows:

Refrigeration medium is introduced into the intake rooms 6F, 6R of thehousing 4F, 4R from the intake part of the outer cooling circuit by theintake effect generated in the cylinder bores 2F, 2R. Then, therefrigeration medium opens the intake lead valve members of the intakevalve sheet 33 and flows into the cylinder bores 2F, 2R from the intakeports 31. The medium is compressed in the cylinder bores 2F, 2R. Due tothe exhaust effect of the cylinder bores, the compressed medium opensthe exhaust lead valve members 21A of the exhaust valve sheet 21 andflows into the exhaust rooms 5F, 5R from the exhaust ports 32. Then, themedium is recycled to the outer cooling circuit. During the exhaustingperiod, the exhaust lead valve members 21A which are deformed by theexhaust pressure of the medium are pressed on the rib members 107 of thegasket 100 which serve as the retainers, and the degree of deformationis restricted so that the failure of the exhaust lead valve members 21Ais prevented. The film of the coating composition may absorb the shockwhen the exhaust lead valve members 21A hit the gasket, reduce the noiseand prevent the failure of the exhaust lead valve members 21A.

The coating composition may, of course be applied to other typecompressors such as reciprocal types and a rotary types (e.g. a vanetype).

The coating composition of the invention may be coated on a seal ring ofthe hydraulic equipment and, due to the lubricity of the film, canreduce resistance to slip while maintaining the sealing properties andprevent the troubles such as the failure of working. In general, thelubricity of the film improves the stick-slip on the film surface andreduces the deformation and flaw of the film.

The coating composition has further advantages such that it has a longpot life, e.g. from two weeks to one month, and that even when thecontent of the fluorine-containing rubber is as high as 60% by weight,it can be spray coated without cobwebbing and affords thick film easily.

The present invention will be illustrated in detail by the followingExamples wherein % and parts are by weight unless otherwise indicated.

EXAMPLES 1 TO 7 AND COMPARATIVE EXAMPLES 1 TO 4 Non-adhesiveness of FilmSurface

The following composition A (containing 166 parts of the aqueousdispersion of fluorine-containing rubber) and the following compositionB (10 parts) were homogeneously mixed and filtered through a 200 meshwire mesh to prepare an aqueous fluorine-containing rubber coatingcomposition:

    ______________________________________                                                           Part(s)                                                    ______________________________________                                        Composition A                                                                 Aqueous dispersion of                                                                              166                                                      fluorine-containing rubber*.sup.1                                             (the rubber content being 60%, and                                            Nonion HS-208 being contained)                                                Aqueous dispersion of                                                                              amount as shown                                          fluorine-containing resin*.sup.2                                                                   in Table 1                                               (the resin content being 50 or 60%,                                           and Nonion HS-208 being contained)                                            Magnesium oxide       3                                                       Medium thermal carbon                                                                              20                                                       Nonion HS-208         2                                                       (20% aqueous solution)                                                        Water                50                                                       Composition B                                                                 A-1100               40                                                       V-11                 20                                                       Water                40                                                       ______________________________________                                         Note                                                                          *.sup.1 Vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene           elastic terpolymer (hereinafter referred to as the "fluorine rubber").        *.sup.2 Polytetrafluoroethylene (hereinafter referred to as "PTFE") or        tetrafluoroethylene/hexafluoropropylene copolymer (hereinafter referred t     as "FEP").?                                                              

The thus prepared coating composition was spray coated on an aluminumplate (100 mm×50 mm×1 mm) which had been degreased with acetone, driedat a temperature of 50° to 70° C. for ten minutes to form a film of 30μthick and cured at 300° C. (in Examples 1 to 3) or at 380° C. (inExamples 4 to 7 and all Comparative Examples) for ten minutes.

Contact angle of water against the cured film was measured by dropping adrop of purified water on the surface at 24° C. with a goniometer (ElmaKogaku Kabushikikaisha).

The results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                Amount of the                                                                           Rubber/Resin                                                        resin disper-                                                                           (solid content                                                                            Contact angle                                           sion (parts)                                                                            ratio)      (°)                                      ______________________________________                                        Example 1 FEP  60     23/77       103                                         Example 2 FEP 100     33/67       104                                         Example 3 FEP 200     50/50       108                                         Example 4 PTFE  50    23/77       110                                         Example 5 PTFE  83    33/67       113                                         Example 6 PTFE 167    50/50       116                                         Example 7 PTFE 250    60/40       116                                         Comparative                                                                             0            0/100       76                                         Example 1                                                                     Comparative                                                                             0            0/100       99                                         Example 2                                                                     Comparative                                                                             FEP 400     67/33       *1                                          Example 3                                                                     Comparative                                                                             PTFE 388    72/28       *1                                          Example 4                                                                     ______________________________________                                         Note:                                                                         *1 Pinholes or cracks formed even at 10μ  thick, and no film was           obtained.                                                                

EXAMPLES 8 TO 14 AND COMPARATIVE EXAMPLES 5 AND 6 Lubricity of FilmSurface

Friction coefficients of the film obtained in Examples 1 to 7 andComparative Examples 1 and 2 were measured by a Bowden-Leben typeequipment under the following conditions: temperature, 24° C.; steelball, 8 mm; load, 250 g; linear speed, 0.2 cm/sec.

The results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                             Friction coeffi-                                                     Film     cient                                                    ______________________________________                                        Example 8     Example 1  0.47                                                 Example 9     Example 2  0.36                                                 Example 10    Example 3  0.27                                                 Example 11    Example 4  0.23                                                 Example 12    Example 5  0.19                                                 Example 13    Example 6  0.08                                                 Example 14    Example 7  0.07                                                 Comparative   Comparative                                                                              0.70                                                 Example 5     Example 1                                                       Comparative   Comparative                                                                              0.40                                                 Example 6     Example 2                                                       ______________________________________                                    

EXAMPLES 15 TO 17 AND COMPARATIVE EXAMPLES 7 TO 9 Bonding test

The following composition A' (100 parts) and the following compositionB' (5 parts) were homogeneously mixed and filtered through a 200 meshwire mesh to prepare an aqueous fluorine-containing rubber coatingcomposition:

    ______________________________________                                                              Part(s)                                                 ______________________________________                                        Composition A'                                                                Aqueous dispersion of the fluorine                                                                    166                                                   rubber (the rubber content being 60%,                                         and Nonion HS-208 being contained)                                            Aqueous dispersion of FEP                                                                             60                                                    (FEP content being 50%, and                                                   Nonion HS-208 being contained)                                                Magnesium oxide          3                                                    Medium thermal carbon   20                                                    Water                   50                                                    Composition B'                                                                Aminosilane compound    90                                                    (as shown in Table 3)                                                         Water                   10                                                    ______________________________________                                    

The thus prepared coating composition was spray coated on an aluminumplate (100 mm×50 mm×1 mm) which had been degreased with acetone or aniron plate (100 mm×50 mm×1 mm) which had been degreased with acetone andblasted with 80 mesh Tosa emery at a wind pressure of 5 kg/cm², anddried at a temperature of 50° to 70° C. Then, spraying and drying wererepeated three times to obtain a film of 100 to 150μ thick. The film wascured at 150° C. for thirty minutes.

The cured film was cut into strips of 100 mm wide with the depth to thesurface of the metal plate as the substrate. The 180° peeling test wasconducted at 24° C. by peeling the end of the strip with an autograph"Shimadzu IS-500" at a rate of 50.0±2.5 mm/min.

The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                            Peeling strength                                                              (kg/cm)                                                          Aminosilane or amine                                                                         Aluminum  Iron                                          ______________________________________                                        Example 15                                                                             A-1100           0.81*.sup.3                                                                             1.01*.sup.3                               Example 16                                                                             A-1100           0.63*.sup.3                                                                             0.61*.sup.3                               Example 17                                                                             A-1600*.sup.1    0.24*.sup.3                                                                             0.28*.sup.3                               Comparative                                                                            A-1125*.sup.2    Coating impossible                                  Example 7                 due to gellation                                    Comparative                                                                            N,N--Dicinnamylidene-                                                                          0.17*.sup.4                                                                             0.16*.sup.4                               Example 8                                                                              1,6-hexanediamine                                                    Comparative                                                                            V-11             0.05*.sup.4                                                                             0.07*.sup.4                               Example 9                                                                     ______________________________________                                         Note:                                                                         *.sup.1 NH.sub.2 CONH(CH.sub.2).sub.3 Si(OCH.sub.2 CH.sub.3).sub.3.           *.sup.2 CH.sub.3 CO(CH.sub.2).sub.2 NH(CH.sub.2).sub.2 NH(CH.sub.2).sub.3     Si(OCH.sub.3).sub.3 (an aminosilane compound having no terminal amino         group).                                                                       *.sup.3 The film was destroyed.                                               *.sup.4 Ply separation.                                                  

EXAMPLES 18 TO 21 AND COMPARATIVE EXAMPLES 10 AND 11 Tensile strength offilm

A fluorine-containing rubber coating composition was prepared by mixingthe composition A as used in Example 1 (containing 166 parts of theaqueous dispersion of the fluorine rubber) and the compositions B(amount as shown in Table 4) but containing A-1100 and V-11 in aproportion as shown in Table 4. In Example 18 and Comparative Examples10 and 11, the composition B containing 0.01 mol of a mixture of A-1100and the amine in a molar proportion of 1:1 was added to the compositionA containing 166 parts of the aqueous dispersion of the fluorine rubber.

The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                               Composi-               Tensile                                                tion B   Aminosilane/Amine                                                                           strength                                               (parts)  (molar ratio) (kg/cm.sup.2)                                   ______________________________________                                        Example 18                                                                             --         A-1100/V-11   72                                                              (1/1)                                                     Example 19                                                                             10         A-1100/V-11   92                                                              (72/28)                                                   Example 20                                                                             15         A-1100/V-11   101                                                             (72/28)                                                   Example 21                                                                             20         A-1100/V-11   111                                                             (72/28)                                                   Comparative                                                                            --         A-1100/Benzidine                                                                            15                                          Example 10          (1/1)                                                     Comparative                                                                            --         A-1100/V-3*.sup.1                                                                           13                                          Example 11          (1/1)                                                     ______________________________________                                         Note:                                                                         *.sup.1 N,N--Dicinnamylidene1,6-hexane-diamine.                          

EXAMPLE 22 Pot life, spray coating and coated piece test

In the same manner as in Example 1, an aqueous fluroine-containingrubber coating composition was prepared from the following compositionA" (100 parts) and the composition B (5 parts) as used in Example 1:

    ______________________________________                                        Composition A"          Part(s)                                               ______________________________________                                        Aqueous dispersion of the fluorine                                                                    166                                                   rubber (the rubber content being 60%,                                         and Nonion HS-208 being contained)                                            Aqueous dispersion of FEP                                                                             60                                                    (FEP content being 50%, and                                                   Nonion HS-208 being contained)                                                Magnesium oxide          3                                                    Medium thermal carbon   20                                                    Nonion HS-210 (manufactured by                                                                         2                                                    Nippon Oil and Fats Co., Ltd.)                                                Water                   50                                                    ______________________________________                                    

The thus prepared fluorine-containing rubber coating composition wasstored in a 300 ml volume glass bottle with a cap at 24° C. Even afterten days, no gellation was observed, and the solid components could beredispersed.

The coating compositon was spray coated on a SPCC made gasket of acompressor for an automobile cooler under the following conditions:nozzle diameter, 0.8 mm; spray pressure, 3.0 kg/cm². Spray coating waseffected without any trouble, and a film of about 30μ thick wasobtained.

The obtained coated gasket was assembled in a compressor with a pressureof 300 kg/cm², and the compressor was operated at an exhaust gastemperature of about 120° C. (thus the gasket being exposed to the gasof 120° C.) for 500 hours. After operation, the compressor wasdisassembled. The gasket was easily removed from the seal surface,hardly swelled with the refrigeration medium (Flon gas R-12) and therefrigerator oil. The gasket was reusable.

For comparison, a gasket coated with a conventional fluorine-containingrubber or a gasket coated with nitrile rubber and treated with graphitein order to prevent bonding was assembled in a compressor, and thecompressor was operated under the same conditions as above. Afteroperation, the gasket was disassembled. In the case using theconventional fluorine-containing rubber, the gasket was bonded to theseal surface. It was difficult to remove the gasket, and a part of therubber was peeled off. Thus, the gasket was not reusable. Further, therubber was squeezed out beyond the circumference of the gasket. Also, inthe case using the nitrile rubber, the rubber was squeezed out beyondthe circumference of the gasket.

When the squeezed-out parts of the rubber exit during the operation ofthe compressor, they may form foreign particles in the circuit and bitethe sliding surfaces and the surfaces of the valve sheet, which maycause trouble in operation.

EXAMPLE 23 Recovery from compression

The following composition A"' (containing 166 parts of the fluorinerubber) and the composition B as used in Example 1 (30 parts) were mixedto make an aqueous fluorine-containing rubber coating composition:

    ______________________________________                                        Composition A'"         Part(s)                                               ______________________________________                                        Aqueous dispersion of the fluorine                                                                    166                                                   rubber (the rubber content being 60%,                                         and Nonion HS-208 being contained)                                            Aqueous dispersion of FEP                                                                             60                                                    (FEP content being 50%, and                                                   Nonion HS-208 being contained)                                                Magnesium oxide          3                                                    Medium thermal carbon   20                                                    Fibrous potassium titanate                                                                             6                                                    Nonion HS-208            2                                                    (20% aqueous solution)                                                        Water                   110                                                   ______________________________________                                    

The coating composition was spray coated on an iron plate to form aneven film of about 50μ thick. On the film surface, a metal ring wasplaced and heat pressed at 150° C. under a pressure of 300 kg/cm² forfive minutes. After the ring was removed, no ring mark was observed onthe pressed surface of the film. However, when a conventional aqueousfluorine-containing rubber coating composition (same as the compositionA but not including the fluorine-containing resin and fibrous potassiumtitanate) was used, ring mark was observed on the pressed surface.

What is claimed is:
 1. An aqueous fluorine-containing rubber coatingcomposition comprising (a) fluorine-containing rubber, (b)fluorine-containing resin, (c) an aminosilane compound of the formula:##STR3## wherein R is methyl or ethyl; X is a single bond or --(CH₂)₂--NH--, --CONH-- or --(CH₂)₂ --NH--(CH₂)₂ --NH--; and n is 2 or 3, and(d) an aqueous liquid vehicle, the weight ratio of the component (a) andthe component (b) being from 95:5 to 35:65.
 2. The coating compositionaccording to claim 1 wherein the weight ratio of the aminosilanecompound and the fluorine-containing rubber is from 1:100 to 30:100. 3.The coating composition according to claim 1 comprising additionally aninorganic fibrous material.
 4. The coating composition according toclaim 1 or 3 further comprising an amine compound having at least oneterminal amino group directly attached to a hydrocarbon group.
 5. Thecoating composition according to claim 1 wherein the amine compound hasat least two terminal amino groups.
 6. The coating composition accordingto claim 4 wherein the molar ratio of the aminosilane compound and theamine compound is from 1:99 to 90:10.
 7. The coating compositionaccording to claim 1 wherein the aminosilane compound is partly orcompletely prehydrolyzed.
 8. The coating composition according to claim3 wherein the inorganic fibrous material is glass fibers, carbon fibers,asbestos fibers or fibrous potassium titanate.
 9. An article coated withthe aqueous fluorine-containing rubber coating composition according toclaim
 1. 10. The article according to claim 9 which is a gasket.
 11. Thearticle according to claim 10 wherein the gasket is a metal-made gasket.12. The article according to claim 11 wherein the metal is iron,aluminum or copper.
 13. A coating composition according to claim 1,wherein said fluorine-containing rubber component (a) is a fluorinatedelastic copolymer comprising about 40 to 85% by mol of units ofvinylidene fluoride and about 60 to 15% by mol of units of at least oneother fluorine-containing ethylenically unsaturated monomercopolymerizable therewith.
 14. A coating composition according to claim1, wherein said fluorine-containing resin component (b) ispolytetrafluoroethylene or a copolymer of polytetrafluoroethylene and atleast one ethylenically unsaturated monomer.
 15. A coating compositionaccording to claim 14, wherein said ethylenically unsaturated monomer isan olefin, a haloolefin, or a perfluoro(alkyl vinyl ether).
 16. Acoating composition according to claim 15, wherein said ethylenicallyunsaturated monomer is hexafluoropropylene, perfluoro(methyl vinylether), perfluoro(ethyl vinyl ether) or perfluoro(propyl vinyl ether).17. An aqueous fluorine-containing rubber coating composition havingimproved non-adhesiveness and lubricity characteristics comprising (a) afluorinated elastic copolymer comprising about 40 to 85% by mol of unitsof vinylidene fluoride and about 60 to 15% by mol of units of at leastone other fluorine-containing ethylenically unsaturated monomercopolymerizable therewith, (b) a polytetrafluoroethylene or a copolymerof polytetrafluoroethylene and at least one ethylenically unsaturatedmonomer, (c) an aminosilane compound of the formula: ##STR4## wherein Ris methyl or ethyl; X is a single bond or --(CH₂)₂ --NH--, --CONH-- or--(CH₂)₂ --NH--(CH₂)₂ --NH--; and n is 2 or 3, and (d) an aqueous liquidvehicle, the weight ratio of the component (a) and the component (b)being from 95:5 to 35:65.
 18. The coating composition according to claim17, wherein the aminosilane compound is partly or completelyprehydrolyzed.
 19. An article coated with the aqueousfluorine-containing rubber coating composition according to claim 17.20. A gasket coated with the aqueous fluorine-containing rubber coatingcomposition according to claim 17.